package com.lara;
import java.util.ArrayList;
import java.util.List;

public class DuplicateNumber
{
	public int findDuplicateNumber(List<Integer> numbers)
	{
		int highestNumber = numbers.size()-1;
		int total = getSum(numbers);
		int duplicate = total-(highestNumber*(highestNumber+1)/2);
		return duplicate;
	}
	public int getSum(List<Integer>numbers)
	{
		int sum = 0;
		for(int num:numbers)
		{
			sum = sum + num;
		}
		return sum;
	}
	public static void main(String[] args)
	{
		List<Integer>numbers = new ArrayList<Integer>();
		for(int i = 1; i<30; i++)
		{
			numbers.add(i);
		}
		numbers.add(29);
	//	numbers.add(11);
	//	numbers.add(11);
	//	numbers.add(9);
		DuplicateNumber dn = new DuplicateNumber();
		System.out.println("Duplicate Number:" + dn.findDuplicateNumber(numbers));
	}
}